Constant-temperature heater for sheet-glass-drawing machines



1,641,807 Sept 6 1927' w. A. GIBSON CONSTANT TEMPERATURE HEATER FOR SHEET GLASS DRAWING MACHINES original Filed March 2, 1923 2 sheets-sheet 2 ATTO RN E T Patented Sept. 6, 1927".

WILLIAM A. GIBSON, OF CHARLESTON, WEST VIRGINIA, ASSIGNOR T0 THE LIBBEY OWENS SHEET GLASS COMPANY, OF TOLEDO, OHIO, A CORPORATION OF OHIO.

CONSTANT-TEMPERATURE HEATER FOR SHEET-GLASS-DBAWING MACHINES.

Application filed March 2, 1923, Serial No. 622,252. Renewed March 22, 1926.

This invention relates to a 'temperature stabilizing system, and more particularly to a constant temperature heating means especially adapted for use in connection with sheet-glass drawing machines.

In machines of this type, it is necessary to maintain certain fixed temperatures at certain points in the apparatus, or in certain chambers, and it is desirable to have these temperatures remain as steady and constant as possible; The glass sheet during its formative period is very susceptible to slight changes in temperature, and the steadier the temperature controls the more uniform the sheet produced. With the 4gas flames customarily used it is diflicult to obtain either the exact temperature desired, or a constant degree of heat, due to variations in the gas pressure and the quality of the gas.

The object of the present invention is to provide such a heating means with a definite and constant temperature. v Use is made of the well-known property o'll certain materials that, while in transition from the solid to the `liquid state, or vice-versa, the temperature will remain constant until all of the material has been melted or solidified. A certain 4amount of latent heat is absorbed by the material in changing it from the solid to the liquid form. Ifj the temperature of the melted material is higher than that of the surrounding substances, it will gradually solidify and give out this heat to the cooler substances, but will retain the same constant temperature until all of the material is solidified. In utilizing this principle to a practical end, a materlal is selected whose lnelting point is slightly higher than the temperature to be maintained in the adjacent chamber or objects therein. The material will thus act as a heater for the cooler objects, and the difference in temperature should just balance the heat lost by radiation or carried away by the heated objects. This selected material is enclosed in a suitable container, and is constantly maintained in a partially melted condition by applying heat thereto from an outside source. Automatic means are provided for turning this heat on or oft as required.

The invention will be better understood from the following detailed description of' one approved form of the apparatus. In the accompanying drawings:

Fig. 1 is a longitudinal vertical section through the flattening chamber of a sheet glass drawing machine, showing this invention applied thereto.

Fig. 2 is a transverse vertical section through the apparatus, taken substantially on the line 2-2 of Fig. 1.

Fig. 3 is an elevation of the automatic liurner controller, looking from the left at Fig. 4 is a transverse section similar to Fig. 2 through the container for the melted material, showing a modified form of heatinfr means.

In the example here illustrated, the invention is applied to the flattening table of a sheet glass machine of the Colburn type, as substantially described and illustrated in the patent `to I. W. Colburn, 1,248,809, granted Dec. 4, 1917. In this apparatus the sheet of glass 1, is drawn up from the mass of molten glass 2, in receptacle 3, and bent over the bending roller 4 into the horizontal. It then passes over the supporting rollers 5 and 6 into the flattening chamber 7. The sheet is carried through this chamber on the endless chain of intermeshing links 8, which form a drawing and flattening table. The upper run of this table of intermeshing links is slidably supported in a flat and horizontal position upon the stationary table 9. The chain-loop 8 is carried at its ends by sprockets 1() and 11. A second endless loop of draw-bars 12, carried by sprockets 13 and 14, rests in its lower run upon the edges of the glass sheet 1, holding the sheet down in frictional contact with the table 8. The loops 8 and 12 are driven at suitable speeds by the sprockets 1() and 13 so that the glass sheet is steadily drawn through the chamber 7 from which it passes into the leer. While the sheet is upon the table 8 it becomes flattened and set in its final form. All ofthe above is old, as described more in detail in the Colburn patent noted above.

The sheet 1 enters the chamber 7 at one temperature, loses a certain amount of heat while passing through the chamber, and emerges at a somewhat lower temperature. Meanwhile the chamber 7 and the parts located therein are losing heat through radiation and conduction. To maintain this range of temperatures constant it is necessary to supply a certain amount of heat to the chamber 7, to offset these temperature :Evi

a constant temperature of 10000 F. within the chamber, and itis found 'that if this large mass of material (the heat stabilizing body), has a constant temperature of 10100 F., the heat given out to the chamber l5 will just compensate for the temperature losses in the chamber and maintain same at a constant vtemperature of 10000 F. lt is found by experiment, or by consulting re- Search tables, that an alloy of 67% aluminum and 33% copper has its melting point at 10100 F. Accordingly the. hollow table 9 is substantially filled with this alloy.

Let us assume the mass ott alloy 15l to be in a molten condition, but no further heat is being added thereto. The alloy will commenceto solidify, gradually4 giving out `its latent heat of crystallization to the chamber 7 and .objects therein. However, the mass lvremains at its fixed temperature of 10100 F. as long as anyof the material remains in a molten state. Before this solidi tying or crystallizing process is entirely completed, heat is applied to the mass 15-and it is again slowly melted. This heating means may takeany convenient form. As shown `inaitter. Tn any case, the heating eHect of in Figs. 1 to 3, a small group of gas burners 16 are arranged centrally beneath the container 9.V lin Fig.` 4, electric heating elements 17 are embodied within thecontainer 9, as will be morespecifically described herethese primary heating devices should be confined as tar as possible to the mass of material 15. All 'the while the material is being 5 melted, it still retains its melting temperature of 10100 F. and is giving out heat to the chamber 7 at the same rate as while -crystallizingl The primary heaters 16 and '17 need not be large, but only sufficient to 0 add more heat to the material than is being simultaneously given out to the chamber 7. Before the material l5 is entirely melted the primary heater 16 or 17 is turned oli', and the material again commences to solidify. This cycle is repeated indenitely, the mass 15 remaining at a constant temperature of 10100 F. and constantly giving od" heat at a fixed rate to the chamber 7, and sheet 1 therein.

lt is desirable to provide some automatic means for turning the primary heating device 16 on or otl at the proper times. Tn the example here shown, advantage is taken of they tact that materials change volume or density when passing trom the liquid to the solid or viceversa. Most mate- Leanser rials or metals that would be usedvin this apparatus have a greater volume when molten than when in the solid state. The container 9 is hermetically` seal/ed, and the slight airspace 18 above the materiall is in communication through pipe 19 with a sensitivev diaphragm 20, mounted on a frame 21 outside ot the machine. The diaphragm 20 is connected through link 22 with a'lever 23, pivoted at one end 24 to the supporting frame 21, and carrying a pair of switch contacts 25 and 2,6 at theopposite sides'of its free end. A light spring 27, mounted between the diaphragm and a branch 281 of frame 21, helps compress the diaphragm land swing the lever `to the left when the pressure decreases within the diaphragm. The contacts 25 and 26 on the lever 23 cooperate with a pair of contacts 29 and 30, adjustably mounted yon the bar` 31. This bar 31 is .mounted for a limited longitudinal sliding movement in the frame 21, its travel in either direction being limited by the stops 32 and 33,-which engage adjacent portions of the supporting trame.

The gas for burners 16 passes from supply pipe' 34 through ,valve 35, and pipe 36 to the burners. The valve 35 is of a type that may be turned on or ofi by valve stemythrough approximately 900, and

oscillating the this valve is controlled by the gear segment l 37, in mesh with the rack 38 on the rod or core 39 of the two oppositely acting solenoids 40 and 41 carried by the frame 21. p

When solenoid 40 is energized,` the core 39 willbe drawn thereinto, turning the valve tothe left, which is the open position, as shown in Fig. 3. Justbefore the core 39 com letes its travel to the left, the lug 42 ont e4 core engages the lug 43 on slide 31, and shifts the slide 31 to the left until stop 32 engages the -trame 21.v When solenoid 41 is energized, the core 39 will be drawn to the right, closing the valve. Just before the core reaches the end of its throw to the right, the lu 42 engages the lug 44 on slide 31, and shi ts the slide to the right" until stop 33 engages the frame 21.

The lead 45 from the "positive main connects with the contacts 25 and 26 on swinging lever 23. Contact 29, on slide 31, is connected by wire 46 with'one end of solenoid 40. The other contact 30 on the slide is connected by wire 47 with one end of solenoid 41. The opposite ends of the two solenoids are `connected by wires 48 and 49 with the negative main. All of this is indicated in Fig. 3. f

Tn operation, we will assume that the primary heating means has been turned ott', and that the molten alloy 15 has been soliditying, and giving ott its latentheat to the adjacent substances. As the material 15 freezes or crystallizes, it shrinks, and the pressure on diaphragm 20 is relieved and i the softening point oitl the'mntainer 9.

the lever 23 gradually swings to the left, Fig. 3. Before the material 15 has entirely crystallized, contact 25 engages Contact 29. A circuit is now completed from the positive main through Wire 45, contacts 25 and 29, wire 46, solenoid 40, and Wire 48 to the negative main. Core 39 will be drawn to the left and the valve 35 opened and the gas turned on. A constantly burning pilotlight, or lights 50, fed through pipe 51, from below the valve 35, Will ignite the burners 16. Just before core 39 completes its movement to the left, lug 42 engages lug 43, and the slide 31 is shifted slightly to the left breaking the circuit at 25 an 29, and deenergizing' solenoid 40. This is the position oft the parts illustrated inv Fig. 3. The material l5 now commences to melt, and consequently increases its volume. This increases the air pressure in diaphragm 20, and the lever 23 is gradually swung over to the right (Fig. 3), until contact is made between 26 and 30 just before the material is entirel melted. Current now flows from `the positive main through Wire 45, contacts 26 and 30, Wire 47, solenoid 41, and Wire 49 to the negative main. The solenoid 41 will be energized and the core 39 drawn to the right, closing valve 35 and turning oit' the gas burners 16. J ust before the core reaches its limit of movement to the right, lug 42 engages lug 44 and shifts slide 31 until sto 33 engages frame 21. This again breahs the circuit and. deenergizes solenoid 41. The material 15 now commences to solidi-ity again, and the cycle of events just described is repeated. By properly adjusting contacts 29 and 30 along the slide 31, the controller can be timed as desired. Obviously, the construction of this automatic controlling device for the valve 35 is susceptible of considerable variation, and equivalent devices for performing the same function may be susbtituted.

1n the modified form of apparatus shown in Fig. 4, electric heating grids or elements 17 are enclosed Within the mass of material 15 Within the container. r1`his will insure that the full heating effect of the elements is imparted to the material 15. The main switch for turning on or od" the current to the elements 15 may be operated by the mechanism illustrated in lig. 3 for controlling' valve 35, or some equivalent mechanism.

lt should be understood that the temperatures assumed in the above description, as Well as the specific alloy referred to, were described merely by Way of example, and this apparatus is capable of use throughout a Wide range of temperatures. 1t is only necessary that the material 15 be capable ot being melted by some reasonable means, and that the temperature not be higher than The temperature range runs from this point down to any temperature above normal, that is the `material should be one that is solid at normal temperatures. Metals or alloys By varying the proportions in certain alloys, materials having melt-ing points at practically any intermediate temperatures may be located. For example, in the aluminum-silicon alloys, the melting point will vary with the percentage of silicon approximately as follows:

Per cent silicon. Melting point. 0 1220 F. 1 1211 l0 1094 1l 1076 1l 6 1068 Vith a higher percentage of silicon-the melting point rises again. The use of a eutectic composition (that is, one of lowest melting point) such as the alloy of 11.6% silicon, and 88.4% aluminum, is preferred, but not necessary, in this apparatus. By first selecting the proper metals, and then varying the percentages in the alloy, one having a melting point at. practically any temperature ma be determined.

It is to be un erstood that the application of this temperature regulator to tlie flattening chamber of the sheet-glass drawing machine is merely one use oi the device presented in detail as an example. The same system may easily be adapted to other parts of the same machine, or other inachines, Wherever a steady' and uniform temperature is desirable.

l claim:

1. The method ot controlling the temperature in a chamber, consisting in maintain- .ing an adjacent. mass ol material in a partially melted condition.

2. The method of controlling the temperature ot' a glass sheet, consisting in maintaining an adjacent mass ot material in a partially melted condition.

iso

3. A temperature stabilizer comprising a when the material changes from a liquid to body of normally solid material maintained a solid state or vice-Versa, and means conin transition between the solid and liquid trolled by the diaphragm for turning on the states. latter heating means before the material 4. A temperature stabilizer comprising a entirely solidilies), and .turning olf this heatmass of metallic, substance maintained in ing means before the material is entirely Vtransition between the solid and liquid melted. p

states. 14. In a sheet glass drawing. machine, a

5. A means for maintaining a constant hollow flattening table for the sheet, a mass i0, temperature comprising a mass of normally f material in the table whose melting point 75 a partially melted condition.

partially melted condition.

solid material whose melting point is Someis slightly higher than the temperature at, what higher than the desired temperature, which the sheet is to be maintained, land and means for maintaining this material in means for keeping the material in a partially a partially solid and partially liquid C011-,| melted condition. dition. i 15. In a sheet glass drawing machine, a 6. A heatiilg means 0f COIiSt/ant tem eI- hollow container adjacent the path of travel ature comprising a mass of material w ose 0f the Sheet, a magg 0f material in the eenmelting point is at the desired temperature, rainer Whose melting point is Slightly higher and means for lmaintaining this material in than the temperature at which the sheet is to be maintained, and means for keeping the 7 A heating means 0f COHStaIit tempel material in a partially melted condition. atlile Comprising e mitSS 0f metal WllOSG 16. In a sheet glass drawing machine, a melting point is at the deSiTd temperature, hollow iiatteningtable for the sheet, a mass and means for maintaining this metal in a of material in the table whose melting point is slightly higher than thetemperature at 8. A heating means 0f COIISRD tem elwhich the sheet is to'be maintained, and ature: comprising a maSS 0f materiel WlOSe means for heating the material at intervals melting point is at the desired temperature, te keep it in a partially melted condition. and means for heating the material at 1H- 17. In a sheet glass drawing machine, a

tervals to maintain it in a pl'tiallyfmelted hollow container adjacentthe path of travel condition. of the sheet, a mass of, material inthe con- 9. A heating means of constant tempertainer whose melting point is slightly higher ature comprising a mass of material whose than the temperature at which the Sheet is melting point is at the desired temperature, to be maintained, and means for'heating the and heating means controlled by the Chengmaterial at intervals to keep it in a partially ing volumerof the material, to maintain the melted Condition,

material inv a partially'melted'-condition. v, 18, In a sheet glass drawingmaehine, a 10. A constant temperature heating meaIlS hollow container adjacent the path of travel comprising a hollow container substantially 0f the Sheet., a, mass of material in the com filled with a mass 0f material having itS tainer whose melting point is slightly highermelting point at the desired temperature, than the temperature at which the sheet is to and meails for keepiig the matellai 1n a be maintained, means for heating the matepartaially melted condition rial at intervals to keep it in a partially l1. A COIlStaIlt temperature heating means, melted condition, and means controlled by comprising a hollow' container substantially the Change in Volume of the material befilled With a maSS Of material having "its tweenthe solid and liquid states, to turn the meltingV point at the desired temperature, heating means on or oit. and means forI heating the material at in- 19 In a Sheet glass drawing machine` n teryals to keep it in a partially melted ycoIlhollow container adjacent the path of travel d1t1on. of the sheet, a mass of material in the con- 12- A. Constant temperature heatmg 1.93115 tainer whose melting point is slightly higher comprising a hollow @entamer Substantially than the temperature at which the sheet is filled with a m'SS 0f mettermi heVlHg it to be maintained, means for heating the melting ipomt at the, deslred temperature, material at intervals to keep it in a partially heating means for malntalnmg the material melted condition, and pressure controlled in a. partially melted condition, and means means Operated by the Change in volume of automatically COIllOlled by the Changing 'the material between the solid and liquid volumeof the material to regulate the latter states, which turns the heat off 'before the heating means. material is entirely melted, and turns the 13. A constant temperature heating means heat on `before it has entirely solidified. comprising a hollow container substantially 20A The use of latent heat of melting of filled with a mass of material having its materials as a means of stabilizing temperamelting point at the desired temperature, tures in a glass drawing machine. heating means for melting the material, a 21". ln sheet glass drawing apparatus. diaphragm controlled by the displaced air means to draw a sheet of glass from a lllO chamber, and means for keeping the material in a partially melted condition.

23. In sheet glass apparatus, means for drawing a sheet of glass from a mass of molten glass, including a draw table, and means to automatically and directly maintain the draw table substantially at a predetermined temperature.

Signed at Charleston in the county of Kanawha, and State of 2West Virginia, this 24th day of February, 1923.

WILLIAM A. GIBSON. 

